The best evidence for the existence of God is...

By far the strongest argument for design is the lack of randomness the
universe possesses. If I throw a ball up in the air it will
consistently, predictably, and reliably come back down to the ground
every time (unless I threw it past escape velocity, but I’m not that
strong of course). Atheism and random forces producing random rules and
‘code’ does not predict this. Heck, trying to model the universe by
writing code requires a lot of effort and may lead to the presence of
random errors and bugs (the software may crash due to a mistake in the
code, the ball may get lost from time to time, etc…). Indeed, writing
such elegant and consistent code to consistently and reliably produce
such predictable outcomes without crashing and giving errors requires a
very deliberate effort. Yet the universe is able to reliably produce
predictable outcomes to experiments. It follows very
complicated/sophisticated yet consistent and reliable rules,
interdependent rules that reliably harmoniously work together to
reliably produce often simple outcomes to a given experiment. That’s not
chance, that’s design. Chance predicts nothing. Let me see chance model
the universe on a hard drive without the deliberate effort of an
intelligent designer.

This was my reply. Feel free to add to it, make suggestions, point out my errors, etc.:

Of course atheism doesn't "predict" a universe with a "lack of randomness"; atheism is descriptive, not normative. Perhaps you mean "materialism".

But here's the problem: since we already observe the universe as it is (laws, life, etc.), no one can make a "prediction" about it. At best, you might be able to make a post-diction. But in the case of the argument for design, you're simply advocating a tautology – you can't "predict" anything by simply asserting that the laws of the universe must have required a designer. The very concepts of randomness and chance are products of the laws of the universe – it's nonsensical to talk about the laws themselves arising from chance or randomness. Perhaps they simply ARE, and didn't "arise" from anything at all! We. Don't. Know.

We also don't know whether the laws of physics or various constants could be any different or, if they could, how different they could be. You can't talk about chance or randomness without having some sort of value or range of probability, and for that to apply to the universe itself you'd need to know how many possible variations of the laws and constants there could be. Good luck.

tl;dr – The argument from design requires the assumption that the universe had to have come from something else. That's simply not supported by modern physics. It may have, and it's certainly possible, but it's also possible that the universe is enclosed and, like most conceptualizations of God, simply IS.

An assumption of materialism is what has illuminated our understanding of the universe. Sure, it could be wrong; maybe supernatural explanations will at some point become necessary. But there's not yet a shred of evidence to that effect. Supernatural hypotheses can yield no falsifiable predictions about the observable features of the universe – only assert tautologies based on what is already known. As such, they're epistemologically useless.